What I do not understand is why R3 ever selected the flaps. If he meant to go round at 300 feet agl, he never needed to meet the “contract” requirement to select flaps down.
In deploying them, he washed all the speed margin he had. That left him at the bottom end of the recommended range of 170-150 Kts. That was made significant by the fact of his aircraft being so heavy.
A basic rule of glide approaches is to keep your speed up. What ever sort of landing you are destined for, you must harbour some energy with which to control the event. R3 seems, in effect if inadvertently, to have accepted the temptation to stretch his glide. Should he have trimmed nose down while he selected the flaps and did he forget ?
The SI sought to find human factors to explain his mistakes. They could still have wondered about the HF that is commonly called press-on-itis. If R3 felt he was rusty and had consciously set himself a difficult exercise, he really should have better prepared his escape plan – meaning he should have been ready to go around as soon as the exercise got difficult, rather than at the statutory 300 feet.
What the SI might have noticed is that, as he got to 300 feet, R3 had nearly met all the parameters of the “contract”, even as he lost control of his aircraft.